1. Field of the Invention
This invention relates generally to a digital television receiver and, more particularly, to a method and apparatus to ensure that the digital data controlling the receiver is correct at all times.
2. Description of the Prior Art
Television receivers are now well known in which a portion or all of the relevant signal processing, following receipt of the analog television signal, is performed by digital circuitry. Typically, the signal is received and converted into a digital signal, which is processed in digital form, and then reconverted to an analog signal for display on a color cathode ray tube. Unlike conventional analog signal processing, employing various discrete components having fixed values, digital signal processing involves the retention in memories, registers, and latches of purely numerical values that correspond to the desired settings of the various video parameters, such as brightness, hue, vertical and horizontal sync, linearity, and the like.
The retention of such digital data is not a difficult task in a normal digital processor such as might be found in a computer or the like, however, it does pose a problem in equipment such as a television receiver because the receiver has associated with it not only the digital signal elements but also high voltages and pulses. Thus, a very real problem is presented in that the high voltages present in the television receiver can produce noise and transients in the overall circuit, which can adversely affect the various digital values retained at the several memory and register locations in the digital television receiver. In other words, it is possible that the data retained in the various latches, registers, and memories can be unintentionally rewritten with totally spurious data. When this happens, the receiver circuitry being controlled by this erroneous digital values might be harmed or destroyed.